Design and Performance Evaluation of a Rotary Tillage–Press–Burying Combined Machine for Regulating Maize Straw Spatial Distribution

Conventional rotary straw return results in high straw content and uneven distribution within the shallow seedbed, which adversely affects maize sowing operations. To address this issue, a two-stage combined straw return machine with front-mounted rotary blades and rear-mounted burying fingers was developed, and an equiangular slide-cutting burying finger was designed to match the combined operation. A coupled discrete element model of soil–straw–root stubble-implement interactions was established based on sliding cutting theory, and single-factor tests were conducted to investigate the effects of forward speed, burial depth and slide-cutting angle on straw distribution uniformity, straw mass proportion in the 0–5 cm soil layer and power consumption. Field trials were carried out for validation. The results show that, under optimal parameters, the combined machine reduces the standard deviation of straw distribution by 15.89–23.55% and the straw mass proportion in the 0–5 cm layer by 12.41–13.20% compared with a traditional rotary tiller, with a power increase of 19.01–20.85%. This study provides a quantitative reference for improving seedbed quality following straw incorporation in the black soil region of Northeast China.